A light-emitting diode which emits red light or infrared light is used for various purposes, such as communication, various sensors, night illumination, and a light source for a plant factory.
Accordingly, the need for a light-emitting diode emitting infrared light changes from a light-emitting diode which is primarily focused on high output performance or a light-emitting diode which is primarily focused on high-speed response to a light-emitting diode which is focused on both high output performance and high-speed response. In particular, in a light-emitting diode for communication, since a large volume of optical space transmission is performed, high-speed response and high output performance are indispensable.
As a light-emitting diode which emits red light and infrared light, a light-emitting diode is known in which a compound semiconductor layer including an AlGaAs active layer is grown on a GaAs substrate by a liquid phase epitaxial method (for example, Patent Documents 1 to 4).
Patent Document 4 discloses a so-called substrate-removed light-emitting diode in which a compound semiconductor layer including an AlGaAs active layer is grown on a GaAs substrate by a liquid phase epitaxial method, and the GaAs substrate used as a growth substrate is removed. In the light-emitting diode disclosed in Patent Document 4, when the response speed (rising time) is about 40 to 55 nsec, the output is equal to or smaller than 4 mW. When the response speed is about 20 nsec, the output slightly exceeds 5 mW, and as a light-emitting diode which is manufactured using the liquid phase epitaxial method, high output is obtained at the highest response speed.
As an infrared light-emitting diode which has a high light-emission peak wavelength equal to or greater than 900 nm, an infrared light-emitting diode which uses an InGaAs active layer is known (Patent Documents 5 to 7).